US 20090269841 A1
A cell culture system for the production of cells and cell derived products includes a reusable instrumentation base device incorporating hardware to support cell culture growth. A disposable cultureware module including a cell growth chamber is removably attachable to the instrumentation base device. The base device includes microprocessor control and a pump for circulating cell culture medium through the cell growth chamber. The cultureware module is removably attached to the instrumentation base device. Cells are introduced into the cell growth chamber and a source of medium is fluidly attached to the cultureware module. Operating parameters are programmed into the microprocessor control. The pump is operated to circulate the medium through the cell growth chamber to grow cells or cell products therein. The grown cells or cell products are harvested from the cell growth chamber and the cultureware module is then disposed.
1. A cell culture system for the production of cells and cell derived products comprising:
a reusable instrumentation base device incorporating hardware to support cell culture growth; and
at least one disposable cell cultureware module removably attachable to said instrumentation base device, said module including a cell growth chamber.
2. The cell culture system of
3. The cell culture system of
4. The cell culture system of
5. The cell culture system of
6. The cell culture system of
7. The cell culture system of
8. The cell culture system of
9. The cell culture system of
10. The cell culture system of
11. The cell culture system of
12. The cell culture system of
13. The cell culture system of
14. The cell culture system of
15. A method for the production of cells and cell products in a highly controlled, contaminant-free environment comprising the steps of:
providing at least one disposable cultureware module, said module including a cell growth chamber;
providing a reusable instrumentation base device incorporating hardware to support cell culture growth, said base device including a microprocessor control and a pump for circulating cell culture medium through the cell growth chamber;
removably attaching said at least one cultureware module to said instrumentation base device;
introducing cells into the cell growth chamber;
fluidly attaching a source of cell culture medium to said at least one cultureware module;
programming operating parameters into the microprocessor control;
operating the pump to circulate the cell culture medium through the cell growth chamber to grow cells or cell products therein;
harvesting the grown cells or cell products from the cell growth chamber; and
disposing of said at least one cultureware module.
16. The method of
17. The method of
18. The method of
19. A method for the expansion or growth of cells, comprising introducing cells into the cell growth chamber of the cell culture system of
20. The method of
This application is a continuation of:
International Application No. PCT/US2007/012042, filed May 21, 2007, which claims the benefit under 35 USC §119 of U.S. Application No. 60/802,376, filed May 22, 2006, both of which are incorporated herein by reference in their entirety;
International Application No. PCT/US2007/012051, filed May 21, 2007, which claims the benefit of U.S. Application No. 60/802,376, filed May 22, 2006, both of which are incorporated herein by reference in their entirety;
International Application No. PCT/US2007/012052, filed May 21, 2007, which claims the benefit of U.S. Application No. 60/802,376, filed May 22, 2006, both of which are incorporated herein by reference in their entirety;
International Application No. PCT/US2007/012053, filed May 21, 2007, which claims the benefit of U.S. Application No. 60/802,376, filed May 22, 2006, both of which are incorporated herein by reference in their entirety; and
International Application No. PCT/US2007/012054, filed May 21, 2007, which claims the benefit of U.S. Application No. 60/802,376, filed May 22, 2006; both of which are incorporated herein by reference in their entirety.
1. Field of the Invention
The present invention relates to a method and system that creates a self-contained culture environment, and more particularly to a cell culture system incorporating a disposable cultureware module and a reusable compact instrumentation base device that is capable of expanding cells including primary cells and cell lines as well as patient-specific cells or cells lines in an automated, contaminant-free manner.
2. Description of the Related Art
The anticipated growth of personalized medicine will require new paradigms for the manufacture of therapies tailored to the needs of individual patients. The greatest challenge is expected to come in the area of cell based therapies, especially when such therapies are autologous in nature. In such cases each cell or cell based product will need to be manufactured from scratch for each patient. Manual methods for mammalian cell culture, by their nature, are prone to technician error or inconsistency leading to differences between supposed identical cultures. This becomes especially evident as more and more autologous cells are expanded for personalized therapies. Patient-specific cells, or proteins, are subject to variation, especially when scaled beyond levels that can be managed efficiently with manual methods.
In addition to being labor intensive, the stringent requirements for segregation of each patient's materials from that of every other patient will mean that manufacturing facilities will be large and complex, containing a multitude of isolation suites each with its own equipment (incubators, tissue culture hoods, centrifuges) that can be used for only one patient at a time. Because each patient's therapy is a new and unique product, patient specific manufacturing will also be labor intensive, requiring not just direct manufacturing personnel but also disproportionately increased manpower for quality assurance and quality control functions.
Moreover, conventional approaches and tools for manufacturing cells or cell based products typically involve numerous manual manipulations that are subject to variations even when conducted by skilled technicians. When used at the scale needed to manufacture hundreds or thousands of different cells, cell lines and patient specific cell based therapies, the variability, error or contamination rate may become unacceptable for commercial processes.
Small quantities of secreted product are produced in a number of different ways. T-flasks, roller bottles, stirred bottles or cell bags are manual methods using incubators or warm-rooms to provide environments for cell growth and production. These methods are very labor intensive, subject to mistakes and difficult for large scale production.
Another method, ascites production, uses a host animal (usually a mouse) where the peritoneum is injected with the cells that express the product and are parasitically grown and maintained. The animals are sacrificed and the peritoneal fluid with the product is collected. This method is also very labor intensive, difficult for large scale production and objectionable because of the use of animals. Another method is to inoculate and grow the cells in a small stirred tank or bioreactor or bag-type chamber. The tank provides the environmental and metabolic needs and the cell secretions are allowed to accumulate. This method is costly in terms of facility support in order to do a large number of unique cells and produces product at low concentration.
Another method is to use a bioreactor (hollow fiber, ceramic matrix, fluidizer bed, etc) in lieu of the stirred tank. This can bring facilities costs down and increases product concentration. Biovest International of Coon Rapids, Minn., has or had instruments using these technologies—hollow fiber, ceramic matrix, fluidized bed and stirred tanks.
Cell culturing devices or cultureware for culturing cells in vitro are known. As disclosed in U.S. Pat. No. 4,804,628, the entirety of which is hereby incorporated by reference, a hollow fiber culture device includes a plurality of hollow fiber membranes. Medium containing oxygen, nutrients, and other chemical stimuli is transported through the lumen of the hollow fiber membranes or capillaries and diffuses through the walls thereof into an extracapillary (EC) space between the membranes and the shell of the cartridge containing the hollow fibers. The cells that are to be maintained collect in the extracapillary space. Metabolic wastes are removed from the bioreactor. The cells or cell products can be harvested from the device.
Known EC reservoirs have typically been rigid. They are a pressure vessel and therefore require a sealed compartment with tubing ports adding to costs. A gas, typically air, is introduced through a sterile barrier, generally a membrane filter, to control pressure in the vessel. Fluid level control has been limited to ultrasonic, conductive or optical trip points, or by a load cell measuring the weight of the fluid. Reservoirs are expensive and difficult to manufacture. There is limited EC fluid level measurement accuracy-ultrasonic, conductive or optical monitoring of fluid levels are commonly fouled by cell debris in the reservoir. Alternatively, load cells are not a rugged design for reliable fluid level sensing.
Another problem with the prior art systems is the inability to control lactate and sense pH in the system. One prior art method takes samples of the culture medium and analyzes it using an off-line analyzer. The operator adjusts the perfusion medium rate based on values obtained to maintain the lactate concentration at the level desired. The operator must attempt to predict future lactate levels when adjusting media feed rates. This is labor intensive, presents potential breech of sterility, and the level of lactate control accuracy is dependent on operator skill.
Another method is to connect an automated sampler/analyzer to periodically withdraw sample of the culture media, analyze it and provide feedback for a media feed controller. This method requires additional equipment and increases the risk of sterility breech.
Yet another method is to use an invasive lactate sensor to directly read the lactate level and provide feedback for a media feed controller. In line lactate sensors need to be sterilizable, biocompatible, typically have low reliability and need periodic maintenance.
These methodologies rely on costly, labor intensive off-line sampling and analysis or additional equipment to interface with the instrument or require the addition of a lactate probe and electronics to the culture.
Disposable cultureware generally cannot be autoclaved, so a pH sensor is historically sterilized separately and then added to the cultureware. However, adding the probe risks compromising the sterility of the cultureware. Probe addition is performed in a sterile environment (laminar flow hood) and increases the manpower needed.
The previous methodologies that utilize off-line sampling are subject to contamination problems and depend on the skill of the operator in predicting future lactate levels and influence of media dilution rate. Sampling equipment need interfacing to the culture fluidic circuit, an interface for the feedback signal and periodic calibration of the probes used for sampling. The lactate probe requires interface with the fluid circuit, a method for sterilization or a sterile barrier, interface electronics to convert the probe signal to a useful feedback and a method to calibrate in the fluid circuit.
Preparing the system to start the cell culture is also very labor intensive. The cultureware must be assembled and sterilized or probes must be prepared, sterilized and aseptically inserted into the pre-sterilized portion of the cultureware. The cultureware assembly is then loaded onto the instrument. A series of manual operations are needed to check the integrity of the assembly, introduce fluid into the cultureware flow path, flush the toxic residuals (e.g. surfactants) from the cultureware, start the cultureware in a pre-inoculation mode, introduce factors into the flow path getting it ready for the cells, inoculating the cells into the bioreactor and starting the run (growth of the cell mass and eventual harvest of product).
Two methods are generally used for sterilization. One method places an electrode in a holder, steam sterilizes the assembly (probe) and then aseptically inserts the probe into the pre-sterilized cultureware. The second method involves placing a non-sterile probe into a holder and then using steam to sterilize the electrode in place, referred to as steam in place. Both methods are labor intensive, prone to failure and the procedures need to be validated.
Other methods exist which are less common. Cold sterilants can be used to sterilize the holder and electrode before aseptic insertion. A permeable membrane can be used to isolate the non-sterile probe from the sterile fluid being sensed. A holder with the membrane is placed in the fluid path, either before sterilization or after if the holder and membrane is sterilized separately, and then the sensor is placed against or close to the membrane and the fluid on both sides of the membrane is assumed to be equilibrated.
Glass electrodes have not been included with the cultureware in the past because it was unknown if the probes could survive EtO sterilization and being stored dry. Filled glass electrodes are normally stored hydrated in a liquid buffer.
Each unique cell or cell line must be cultured, cell products harvested and purified separately. In order to do a large number of unique cells or cell lines, a considerable number of instruments would be needed. If application of the cells or products for therapeutic purposes is contemplated strict segregation of each cell production process would be required. Consequently, compactness of the design and the amount of ancillary support resources needed will become an important facilities issue. Moreover the systems currently available are general purpose in nature and require considerable time from trained operators to setup, load, flush, inoculate, run, harvest and unload. Each step usually requires manual documentation.
Moreover, production tracking mandates generation of a batch record for each cell culture run. Historically this is done with a paper-based system and relies on the operator inputting the information. This is labor intensive and subject to errors.
Current purification techniques also involve cleaning and reuse of components. This requires Standard Operational Procedures (SOPs) to be written and the cleaning and reuse process to be validated. This is a time intensive activity.
Accordingly, there is a need for a system and method whereby cells and/or cell products can be cultured in a fully automated, rapid and sterile manner.
One aspect of the present invention is to provide a modular and integrated system for the production and expansion of cells or cell lines. The system consists of a reusable control module housing with all of the mechanical and electronic components and disposable cell growth modules that attach to the control module. This system minimizes the need for skilled technicians and more importantly, prevents the possibility of cross-contamination in a multi-use facility. As an enclosed system, the safety provided by complete segregation facilitates direct applicability to therapies or diagnoses that require autologous cell culture. This self-contained, automated cell culture device allows for simultaneously culture of numerous cell cultures within a compact facility, without the need for individual, segregated cell culture suites. The system of the present invention provides a compact sealed containment system that will enable the cost effective manufacture of cells, cell lines, patient specific cells and cell products on an industrial scale.
Another aspect of the present invention is to provide a method and system that incorporates disposable cultureware, which eliminates the need for cleaning and reuse.
Yet another aspect of the present invention is a system that has the stand-alone integration of a large system in a bench top device (pumps, controls, incubator, refrigerator, cultureware, etc).
Still another aspect of the present invention is a system that incorporates a barcode reader and data gathering software that, when used with an information management system (such as a manufacturing execution system or MIMS), allows for automating generation of the batch record.
Another aspect of the present invention is to provide an EC cycling unit that costs less than rigid reservoirs. Moreover, due to the sealed EC circuit design, without vented reservoir, the chance of cell contamination is minimized.
Still another aspect of the present invention is to provide a system that controls lactate concentration in a perfusion cell culture system using measurement of CO2 and pH.
Yet another aspect of the present invention is to eliminate preparation, autoclaving, and insertion of pH electrodes aseptically in the cultureware which requires a significant amount of time and may breach the sterile barrier of the cultureware set.
The system of the present invention incorporates features that greatly reduce the operator's time needed to support the operations (e.g. integrated pump cassette, pre-sterilized cultureware with pH sensors, quick-load cultureware) and designed automated procedures and apparatuses which allow the system to sequence through the operations (e.g. automated fluid clamps, control software).
The system is capable of integrating the cell culture product production and purification process. The design of the cultureware and instrument simplifies and reduces labor needed to produce product. This reduces sources of error in the process.
The present invention provides an automated cell culture system and method which creates a self-contained culture environment. The apparatus incorporates perfusion culture with sealed, pre-sterilized disposable cultureware, such as hollow fiber or other bioreactors, programmable process control, automated fluid valving, pH feedback control, lactic acid feedback control, temperature control, nutrient delivery control, waste removal, gas exchange mechanism, reservoirs, tubing, pumps and harvest vessels. Accordingly, the present cell culture apparatus (referred to as AutovaxID Cell Culture Module™) is capable of expanding cells in a highly controlled, contaminant-free manner. Cells to which this approach are applicable include transformed or non-transformed cell lines, primary cells including somatic cells such as lymphocytes or other immune cells, chondrocytes, myocytes or myoblasts, epithelial cells and patient specific cells, primary or otherwise. Included also are cells or cell lines that have been genetically modified, such as both adult and embryonic stem cells. Specifically, the automated cell culture apparatus allows for production and harvest of cells or cell-secreted protein in a manner that minimizes the need for operator intervention and minimizes the need for segregated clean rooms for the growth and manipulation of the cells. Further, the apparatus provides a culture environment that is completely self-contained and disposable. This eliminates the need for individual clean rooms typically required in a regulated, multi-use facility. Control of fluid dynamics within the bioreactor allows for growth conditions to be adjusted, e.g. changing growth factor concentrations, to facilitate application of unique culture protocols or expansion of unique cells or cell lines. As a result, there is less variation and less labor required for consistent, reproducible production of cells for applications to expansion of autologous cells and their use in personalized medicine applications.
According to these and other aspects of the present invention, there is provided a cell culture system for the production of cells and cell derived products including a reusable instrumentation base device incorporating hardware to support cell culture growth. A disposable cultureware module including a cell growth chamber is removably attachable to the instrumentation base device.
According to these and other aspects of the present invention, there is also provided a method for the production of cells and cell products in a highly controlled, contaminant-free environment comprising the steps of providing a disposable cultureware module including a cell growth chamber, and a reusable instrumentation base device incorporating hardware to support cell culture growth. The base device includes microprocessor control and a pump for circulating media through the cell growth chamber. The cultureware module is removably attached to the instrumentation base device. Cells are introduced into the cell growth chamber. A source of media is fluidly attached to the cultureware module. Operating parameters are programmed into the microprocessor control. The pump is operated to circulate the media through the cell growth chamber to grow cells or cell products therein. The grown cells or cell products are harvested from the cell growth chamber. The cultureware module is then disposed.
These and other features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiment relative to the accompanied drawings, in which:
The system is based on cell growth chamber technology. For example, bioreactors that have a plurality of semi-permeable hollow fibers or other type of semi-permeable membrane or substrate potted in a housing to create a space inside the fiber or one side of the membrane (referred to as intracapillary or IC space) separate from that outside the fibers or on the other side of the membrane (referred to as extracapillary or EC space). Fluid distribution between the IC and EC space occurs through the fiber pores which can range in size from 10 MW(Kd) to 0.2 μm. Cells are placed on one side of the fiber or membrane, usually in the EC space, in a complete cell culture medium, which is usually the same medium used to expand cells prior to bioreactor inoculation (serum containing, serum-free, or protein-free medium). Cells are usually placed in the EC space when secreted protein is the desired product. In some instances, when cells are the desired product, it may be beneficial to place cells in the IC space.
Medium is perfused through a bioreactor 20 by circulating through the IC space at a fast rate. The medium can be a liquid containing a well-defined mixture of salts, amino acids, and vitamins that often contains one or more protein growth factors. This serves to deliver nutrients to the cell space and conversely, removes or prevents a toxic build-up of metabolic waste. During this circulation, medium is passed through an oxygenator or gas exchanger cartridge 24 which serves to provide pH control and oxygen for the cells and conversely, remove carbon dioxide from the culture. When the bioreactor 20 contains a smaller number of cells, just after inoculation, the oxygenator or gas exchange cartridge is used to provide CO2 and subsequently control pH of the culture environment. As cell number increases, the oxygenator is used to remove CO2 which serves to enhance acid neutralization and control the pH of the culture. Other bioreactor configurations, in addition to hollow fibers, that are designed and optimized for the growth and production of cells and production of cell-derived products are also included.
The system 10 provides significant efficiencies and cost reduction through its disposable component and enclosed operation. As such, cell lines are contained in a closed system and continuously cultured without the need for specialized, segregated clean rooms. This fully integrated apparatus eliminates the need for cleaning and sterilization validations, as well as the need for hard plumbing associated with conventional cell culture facilities.
Referring again to
The one-time use cultureware module 12 is provided pre-sterilized. It is designed for quick loading onto the instrument (“quick-load”), as will be described further herein. The loading of the cultureware body makes connections to the instrument. Pump cassette 70 (
Cell expansion and subsequent process tracking mandates generation of a batch record for each culture. Historically this is done with a paper-based system that relies on operator input of the information. This is labor intensive and subject to errors. The fully integrated device incorporates a barcode reader and data gathering software which, when used with the information management system (MES), allows for automatic generation of the batch record.
The system of the present invention has application in a regulated cell culture environment. It is anticipated that autologous whole cell therapies or patient-specific proteins (vaccines) therapies, would by their nature, require the simultaneous culture of numerous cell lines in a single facility. In addition to the segregation created through this closed culture approach, the apparatus is designed to support a standard information management system (such as a LIMS or MES) protocol. This capability contributes to the creation of thorough batch records and verification of culture conditions to ensure standardization, tracking and safety of each product. This capability facilitates the multi-product concept that is pivotal to facilities involved with autologous or patient-specific products.
As shown in
Gas ports 52 communicate with gas exchanger 24. One port 52 communicates with the input to exchanger 24 and the other port 52 communicates with the output of the exchanger. Gas ports 54 control pressure to the cycling fixture 40. One port 54 communicates with the IC chamber and the other port 54 communicates with the EC space. As viewed from the front, the left port 52 is the exchanger output and the right port 52 is the exchanger input. The top port 54 is the IC reservoir pressurization port, and the lower port 54 is the EC reservoir pressurization port.
As described above, module 12 is heated to maintain cell fluid temperature. Heating mechanism 22 (
When disposable module 12 is installed onto the controlling instrument device 14, the air inlet 88 (
During installation, module 12 is aligned with the connections of the device 14 and the module is placed into the operating position as shown in
As shown in
Typical multi-channel peristaltic pump applications operate using a rotating drive shaft that is common to all rotors. This causes all rotors to turn at the same revolution per minute (RPM), yielding the same fluid output. Different inside diameter tubing may be used to give a fixed ratio delta output from one rotor to another. To obtain a variable output of the peristaltic pump segments, individual pump heads and drives are used. This requires individual tubing cassettes that must be loaded individually and does not allow for close center to center distance between pump heads.
As shown in
The cassette configuration is structured to hold multiple peristaltic tubing segments. A gripping feature 76 on the top and the bottom prevents the tubing from creeping during operation. The design allows for all tubing segments to be loaded into the pump drive mechanism at the same time. A latching feature 74 is also included to provide a bearing surface for the can-operated latch 67 to react upon.
Referring back to
Sterilizable, disposable, actuator driven, rotary selection valves 90 are shown in detail in
The design of this clamp is meant to be used in an automated cell culture application where a disposable cultureware module interfaces with an electro-mechanical instrument. The combined unit is to be automated, which required various tubing lines of the disposable to be occluded/open to provide automated process control. The selector valve is used to automatically open and close tubing lines to direct fluid or gas flow during process control. Minimizing operator set-up is also a requirement. The disposable cultureware must be inserted into the instrument in an operating position with no special operator procedures required for loading the tubing into the clamps. Existing technologies did not meet these requirements, because the manual clamps were not automated, and solenoid valves required a special operator loading procedure.
In the cell culture system of the present invention, the fluid path must be free of unwanted organisms (sterilized). Commercially available selector valves are not gas sterilizable. Sealing surfaces of the selected position may be unexposed to the gas sterilant and those surfaces may be “non-sterile” when the valve is repositioned. Valve 90 provides automated actuation of the cam, compactness, multiple lines, maintains valve position even with loss of actuator power, the disposable valve body is less costly than an equivalent switching valve, and can be incorporated into the back panel of 12. Offset occluded/open cam positioning of two tubing lines can insure a make-before-break switching of fluids. No power is required to maintain any operating position, and tubing segments used in the valve body can be sterilized.
It should be appreciated that a solenoid driven pinch mechanism, can be used in place of the actuator valve. This application may utilize a piston plunger actuated by an electrical coil to provide linear motion to pinch the tubing. A manual pinch clamp could also be used. The clamping position is manually activated by a mechanical bearing surface compressing the tubing and then held in position by a detent feature. This clamp type requires manual deactivation. A membrane over the series of ports could also be used. The membrane is actuated against the port to seal it. Multiple ports are configured for use as a selector mechanism.
In another embodiment shown in
In operation, slide 110 is positioned into slide body 114. Tubing is inserted through tubing ports 108 and slide 110 at position 116 where both tubes are not occluded. A remote servo (not shown) engages into server drive slot 102 and moves the slide to position 117 where one tube is occluded and one tube is not occluded. The remote Servo than moves the slide to position 118 where the occluded tube from the previous step is not occluded, and the tube from the not occluded tube from the previous step is now occluded. When moving the slide from position 117 to position 118, both tubes are occluded to insure that one tube is occluded before the other tube is opened. It should be appreciated that the number of tubes and configuration of the slide can be modified to meet customized applications.
The clamp is meant to be used in an automated cell culture application where a disposable cultureware module interfaces with an electro-mechanical instrument. The combined unit is to be automated, which required various tubing lines of the disposable to be occluded/open to provide automated process control. During process control the clamps are open/closed to simulate the function of an expensive, “disposable” switching valve. Minimizing operator set-up is also a requirement. The disposable cultureware must be inserted into the instrument in an operating position with no special operator procedures required for loading the tubing into the clamps. It provides automated actuation of slide clamp, compactness, multiple lines, maintains clamp position even with loss of actuator power, less costly than an equivalent switching valve. Offset occluded/open position of two tubing lines can insure a make-before-break switching of fluids. No power required to maintain any operating position.
As described above, integrated cool storage area 18 maintains growth factors and harvested cells or cell products at a low temperature (approximately 4° C.). Referring to
As shown in
During operation the pressure is increased in the IC circuit 138 by pressurizing an IC reservoir 137. This pressure causes an ultra-filtrative condition that forces fluid transmembrane across the semi-permeable matrix of the bioreactor 20. The fluid is then forced through the connect tubing, through a flow control valve 133 and into the EC reservoir 130. Externally controlled pressure in the pressure reservoir 132 is allowed to vent. The expanding EC reservoir 130 forces the sensor plate 134 toward the pressure reservoir 132 and compresses it. Sensor plate 134 moves external position flag 140 and this is sensed when EC reservoir 130 has filled enough to expand to the EC upper level. The external position sensor 32 senses this position and the pressure in the IC reservoir 137, is decreased and the pressure in the pressure reservoir 132 is increased. This causes an ultra-filtrative condition and forces fluid out of the EC reservoir through a control valve 135, transmembrane across the matrix of the bioreactor 20 and into the IC circuit 138. The sensor plate 134 moves the external position flag 140 and the sensor 32 senses when the EC reservoir 130 has contracted to the EC low level.
The EC cycling unit of the present invention offers fluid dynamics to cause fluid flow in the EC space thus minimizing nutrient and metabolic waste gradients that may be detrimental to the cells. It provides fluid level control without the use of ultrasonics or load cells that is not affected by cell debris. The flexible reservoirs are considerably less expensive and are suited for disposable applications. The sealed EC reservoir with cycling also limits contamination and isolates the cells.
The present invention also includes an indirect lactate control method for perfusion culture using CO2 and pH sensing. The method predicts open system, perfusion culture, lactate levels in the circulatory medium by monitoring the pH and off-gas CO2 level. This is accomplished by calculating the initial bicarbonate level of the media then utilizing the liquid pH and gas level of CO2 to calculate current lactate concentration. This is used to control media dilution rate of the cell culture. The resulting calculated lactate value is used to set the perfusion rate of media dilution to maintain a pre-determined lactate level. Thus, an invasive sensing system or multiple off-line sampling is not required.
A physical relationship exists between bicarbonate buffer, dCO2, and pH.
Lactic acid production by the cells appears to be the dominant driving force for pH changes in cell culture media. Based on this observation, each mole of lactic acid produced results in consumption of one mole of bicarbonate as described by the following equation:
Equation (3) provides a simple relationship—Henry's Law, that equilibrium dCO2 is proportional to the gas phase concentration of CO2.
Equation (4) is derived by substituting Equation 2 in Equation 1 as follows:
Equation 5 is derived by combining Equations 3 and 4:
The operating equation, Equation (6) is derived by solving for Lactate in Equation (5):
The values of pK and (a) were found to be 6.38 and 0.39, respectively.
Upon taking a lactate and pH reading, the value of (a) is calculated. The initial bicarbonate concentration is calculated as the calibration constant. The advantage is that the bicarbonate concentration does not have to be known when using the present calibration method.
The application is shown in
The present invention utilizes existing signals and with the addition of a non-invasive gas CO2 sensor incorporates lactate control to control media feed rate for cell growth and production. Utilizing the invention reduces materials and labor associated with recurring off-line testing. Utilizing the invention allows for continual adjustment of the dilution rate that would otherwise be inefficient and costly if step increases were used as in previous technologies.
Utilizing the present invention increases the predictability of cell culture metabolics. Allows a perfusion cell culture system to have an increased level of automation. The lactate and media dilution rate can be used to determine the state of cell growth and production.
The present invention also utilizes a novel approach for pH sensing in a cell culture system. Referring back to
In operation the probe 26, for example, a solid gel filled electrode, is mounted in a holder 28 (
Referring to the flow diagram of
As shown in
A bioreactor can be constructed using an outer housing that incorporates a flexible center section. This center section consists of a flexible, non-permeable tubing that allows each end of the bioreactor to be manipulated thus causing movement of the growth matrix. The purpose of this movement is to release the attachment or clumping of cell products on the extra-capillary (EC) side of the fibers. The cell products can then be flushed from the EC via the access port at each end of the bioreactor.
Harvesting cells from a matrix-containing bioreactor such as a hollow fiber bioreactor has been difficult to accomplish. Typically cells are sticky and attach themselves to the fibers or to other cells and form clusters. Rapid flushing of media through the EC to hydraulically force the cells free and into the harvest stream is the most basic method of harvesting cells from the EC space. Typically the quantity of cells harvested is low because the flushing media tends to shunt through the EC and flush cells only from the limited fluid path.
Another method is to physically shake or impact the outer housing to release the cells or clumps of cells. This practice may cause physical damage to the bioreactor or its associated components. Another method includes the use of chemicals to disrupt the adhesion of cells to the fibers or to disrupt the clumps of cells. Adding chemicals to a controlled process may cause adverse effects on cell viability and can introduce an unwanted agent in the down-stream processing.
Some examples for which the system of the present invention can be used are:
At present, the system of the present invention fully integrates the concept of disposable cultureware into automated process control for maintaining and expanding specialized (autologous or other) cell lines for a duration of any time needed. To accomplish this, the system of the present invention was designed for EC space fluid flow that enhances cell growth in high density perfusion culture, yet remains completely closed and disposable. The integrated pre-assembled cultureware, which consists of all tubing, bioreactor, oxygenator, pH probe, is enclosed in a single unit that easily snaps into the apparatus. In addition to this error-proof, quick-load design, the entire cultureware unit enclosed by the casing becomes the cell culture incubator with temperature control regulated through automated process control of the instrument. Pumps and fluid control valves facilitate disposability and error-proof installation, eliminating the possibility of technician mistakes. Finally, during the course of any culture, the closed system has restricted access except for trained and authorized personnel. Manipulations or sampling, outside of program parameters, require password and bar code access before they can be implemented.
Each unique cell line must be cultured, cell secretions harvested and purified separately. In order to manage a large number of unique cell lines, as for example might be required for the production of large numbers of autologous cell therapeutic products or large numbers of unique monoclonal antibodies, a considerable number of instruments would be needed. Compactness of the design and the amount of ancillary support resources needed become an important facilities issue. Small stirred tank systems require a means of steam generation and distribution (for steam-in-place sterilization) or autoclaves to sterilize the vessels and supporting plumbing. To support a large number of units becomes a logistics problem for the facility. The system of the present invention has no such requirement. Larger scale cell culture is historically done in segregated steps that often require separate types of equipment. Manual handling, storage and tracking is needed for all these steps as the culture expands and product is harvested. The method of the present invention integrates these steps into a continuous, fully integrated sequential process. This eliminates the handling risk and facilitates the data gathering required for thorough documentation of the entire process.
Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.